1. Field of the Invention
The present invention relates generally to a rotatable coupling device applied to flexible display screen, and more particularly to a coupling device assembled on an electronic apparatus with a flexible unfoldable/foldable display screen. The coupling device includes a hinge composed of multiple rotary shafts and a responsive structure assembled with the hinge. When the flexible display screen is unfolded/folded along with the hinge, the responsive structure is displaceable relative to the hinge to absorb the deformation amount on inner and outer sides caused by the hinge so as to eliminate the affection of the deformation amount on the flexible display screen.
2. Description of the Related Art
There are various electronic apparatuses provided with covers or display screens, such as mobile phones, notebooks, PDA, digital image capturing devices and electronic books. The covers, display screens or viewers are pivotally mounted on the electronic apparatuses via hinges or rotary shafts, whereby the covers, the display screens or the viewers can be freely rotated and opened/closed under external force. In order to operate the display screen (such as the screen) and/or the apparatus body of the electronic apparatus in more operation modes and application ranges, a conventional dual-shaft mechanism mounted between the display screen and the apparatus body has been developed to rotate the display screen and/or the apparatus body by different angles in accordance with different operation modes.
In recent years, there is a trend to enlarge the size of the display screen, while miniaturizing the volume of the electronic apparatus. In order to meet the harsh requirement, the manufacturers have gradually developed one-piece flexible display to fully cover the two folding leaves of the foldable/unfoldable electronic apparatus. Under such circumstance, in an unfolded state, a large-area display screen can be provided for a user. In the development process, it is found that the conventional hinge (or rotary shaft) cannot be applied to the product of the flexible display screen. This is because in the case that the flexible display screen is assembled and bridged between the two folding leaves of the conventional hinge, the hinge is positioned on one face (inner face or outer face) of the flexible display screen near the middle thereof. When the hinge is pivotally rotated and unfolded/folded, the folding face on the outer side and inner side of the rotational center of the hinge will be inevitably extended or contracted due to the difference between the rotational radiuses. Therefore, when the flexible display screen is disposed on the folding face on the outer side or the inner side of the rotational center of the hinge, which is slightly spaced from the rotational center by a gap, the extension/contraction of the folding face on the outer side and inner side due to the pivotal rotation of the hinge is indirect proportion to the distance between the folding face on the outer side and inner side and the center of the hinge. Also, the extension/contraction of the folding face on the inner side is just reverse to the extension/contraction of the folding face on the outer side. Therefore, in the condition that the flexible display screen is fixed on the inner side or the outer side of the hinge, the deformation amount caused by the extension/contraction of the folding face will inevitably lead to extension or compression of the flexible display screen. This must be overcome. Otherwise, the flexible display screen is inadaptable to the extension/contraction requirement in the unfolding/folding operation and can be hardly applied to such product. Therefore, it is a critical issue how to avoid the extension or the compression of the flexible display screen, which is caused when the conventional hinge is unfolded/folded. This technique decides whether the flexible display screen can be widely applied to the unfoldable/foldable electronic apparatus.
It is therefore tried by the applicant to provide a rotatable coupling device applied to flexible display screen to improve the shortcoming of the conventional technique.